A conventional valve timing control device of this type is disclosed in Patent Document 1 below. This valve timing device has: a drive plate 3 rotatablly mounted on a camshaft 1 subjected to the driving force transmitted thereto from the engine crankshaft 1; a driven shaft member 9 directly mounted on the camshaft 1 and having a conversion guide 11 which is mounted on the circumference of the camshaft 1 and spaced apart from the front face of the drive plate 3; and an intermediate rotational body 5 which is rotatably mounted forwardly of the conversion guide 11 on the driven shaft member 9 via a shaft bearing 14.
The drive plate 3 has radial guides 10, while the driven shaft member 9 has guides 12 which are skewed with respect to the circumference thereof. The intermediate rotational body 5 has a spiral guide 15. Each of the guides 10, 12, 15 is configured in the form of a groove. Each of the skewed guides shares a spherical body 16 with one radial guide 10 and the spiral guide 15 such that the spherical body 16 engages the respective guides. The intermediate rotational body 5 can rotate relative to the driven shaft member 9 when a yoke block 19 coupled with the intermediate rotational body 5 is magnetized by the magnetic field generated by a pair of electromagnetic coils 22a and 22b. 
In the device of the cited Patent Document 1, when the intermediate rotational body 5 is rotated relative to the driven shaft member 9 in the direction of delayed phase angle (the direction hereinafter referred to as angularly retarded direction, and the opposite direction referred to as angularly advanced direction), the spherical body 16 rolls in the spiral guide 15 so that it is inwardly displaced in the radial guides 10 in the form of grooves, thereby effecting cam actions on the conversion guide 11. As a consequence, the coupling angle between the drive plate 3 and driven shaft member 9 integral with the camshaft 1 is varied to the angularly most advanced angle. On the other hand, as the intermediate rotational body 5 is rotated by a magnetic force the angularly advanced direction with respect to the driven shaft member 9, the spherical bodies 16 will roll in the respective guide grooves 15, 10, and 11 in the opposite direction, thereby effecting reverse cam action on the conversion guide 11. As a consequence, the coupling angle between the drive plate 3 and driven shaft member 9 is altered to an advanced phase angle. PATENT DOCUMENT 1: JP No. 3948995